Project Summary/Abstract Pediatric obesity is a public health crisis associated with costly cardiovascular and chronic diseases and decreased quality of life. A disproportionate number of children with obesity, defined as a body mass index (BMI)≥95th percentile for age and gender, are racial/ethnic minorities or socioeconomically disadvantaged. Family-based treatments for childhood obesity have demonstrated effectiveness but struggle with high participant drop-out and inconsistent attendance, limiting opportunities for intervention effects and improving health outcomes. Caregivers frequently drop out due to a program overloading irrelevant information or not meeting their expectations. Due to the complexity of pediatric obesity, contributors to children's weight gain can greatly vary from family to family. Individually tailored family-based programs use rigorous assessment to develop individualized treatment plans that address a family's unique needs and treatment priorities. The Family Check-Up 4 Health (FCU4Health) is an assessment-driven individually tailored family-based pediatric obesity program that targets parenting skills and health behaviors and has had high rates of participation and retention among a low-income predominantly ethnic minority sample. Despite the promise of individual tailoring, tools to quantify the process of individual tailoring are understudied, hindering the ability to evaluate individual tailoring and analyze the theory that tailoring affects program engagement and outcomes. The proposed study will develop and validate an observational rating system to measure the process and degree of individual tailoring in family-based pediatric obesity interventions. Videorecorded sessions, transcripts and multimethod data from a completed trial of the FCU4Health, the Raising Healthy Children (RHC) project, will be used to develop the observational rating system. Next, a second trial of the FCU4Health, the Healthy Communities 4 Healthy Students (HC4HS) project, will be used to validate the new rating system. Finally, scores from the new rating system will be used to test the relationship between individual tailoring, program engagement and changes in health behaviors and anthropometric outcomes using a combined RHC and HC4HS sample. This novel research will employ video observation coding, psychometrics, structural equation modeling, and implementation science methods. The new tool will advance the field of pediatric obesity research by providing a rating system to guide the design, implementation, and evaluation of pediatric obesity interventions with an individual tailoring component. Quantifying individual tailoring will elucidate its relationship with program engagement and outcomes to inform adaptations for evidence-based interventions. The enhanced interventions will accommodate participants' needs, facilitate health behavior change and ultimately prevent and manage pediatric obesity and reduce risk for associated diseases...